Project Summary Resting-state functional magnetic resonance imaging (rsfMRI) is a leading method for the non-invasive characterization of the functional connectivity and resting-state activity of the human brain. In our prior work we have found that rsfMRI measures of connectivity and signal variance can be significantly altered by the subject's vigilance state. Unless these differences in vigilance are taken into account, differences in connectivity strength and signal variance might be interpreted as a disease-related changes. Currently, electroencephalographic (EEG) measures of brain activity are considered the standard approach for the assessment of vigilance. However, their use in rsfMRI studies is limited due to the technical challenges and logistics involved in obtaining simultaneous rsfMRI and EEG measurements. An alternative approach that does not require the acquisition of EEG data would greatly facilitate the assessment of vigilance in a wide range of rsfMRI studies. The goal of this project is to develop and validate an rsfMRI-based measure of vigilance. The aims of the study are to (1) Develop and optimize rsfMRI-based measures of vigilance levels and fluctuations and (2) Perform a preliminary test of the efficacy of the method in a sample of subjects with schizophrenia.